Apparatus for oxygen-filled closedflask combustion



Sept. 29, 1964 I c. L. oecz- 3,150,932

APPARATUS FOR OXYGEN-FILLED CLOSED-FLASK COMBUSTION Filed Sept. 18, 1961 INVENTOR CLYDE L. 066

AITTRNEYS United States Patent APPARATUS FQR GXYGEN-FILLED CLBSED- FLASK COMBUSTIBN Clyde L. (lgg, Philadelphia, Pa assiguor to the United States of America as represented by the Secretary of Agriculture Filed Sept. 18, 1961, Ser. No. 139,011 2 laims. (Cl. 23-253) (Granted under Title 35, US. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to oxygen-filled, closed-flask combustion apparatus in which combustible materials are oxidized as one of the steps in a chemical analysis procedure and has among its objectives providing an improved means of igniting the sample.

The most popular combustion flask for micro-chemical analysis has been an Erlenmeyer flask with a standard taper joint and with the sample holder and ignition unit sealed in the stopper for the flask. The sample, either in a capsule or a folded paper, is placed in the sample holder and the stopper unit inserted in a flask containing a small amount of an appropriate absorbing solution for the determination being made. The flask is charged with oxygen, the flask closed, the sample ignited, and the combustion product taken up in the solution which is then used for making the chemical analysis.

The ignition unit can be a critical factor in obtaining complete combustion of the sample, and, in turn, an accurate analysis of the sample. When capsules are used they must be heated to ignition temperature in less than 3 seconds to prevent the expanding air in the capsule or volatilization of the sample from blowing the capsule apart with the result that some of the sample will not be oxidized.

The ignition unit has typically been an electrical device, for example a high resistance wire, for heating the sample to ignition temperature. Extended use of apparatus with electrical ignition systems has revealed several disadvantages. The electrical contacts in the head of the unit may become loosened, the fuse wire may come loose from the posts, or the glass may crack around the glass to platinum seal. In units in which the sample holder is constructed of wire mesh, the holder becomes brittle and breaks. While tungsten leads may be used in certain determinations, they are not inert to all reaction conditions, for example the phosphorus determination with molybdenum blue reaction, and platinum leads are necessary.

The electrically ignited types do have the safety feature that the sample in the assembled apparatus may be ignited While at a distance from the operator or While enclosed or partitioned off by a protective shield.

An object of the present invention is to provide an apparatus which overcomes the disadvantages of the electrically ignited type, but which retains the safety feature that the sample can be ignited in the flask by remote control.

Another object is to provide a means for rapid ignition of the material to be oxidized.

Other objects and a fuller understanding of the invention may be obtained by referring to the following description and claims taken together with the accompanying drawing in which the sole figure is a side elevation with part cut away for purpose of illustration of a preferred embodiment of the present invention and shows the apparatus and arrangement thereof.

According to the present invention the apparatus for 3,15%,932 Patented Sept. 29, 1964 ice carrying out oxygen combustion in a closed container comprises a transparent container, means for holding the material to be oxidized within the container, a combustible light absorbing material, capable of igniting in less than 3 seconds, and preferably within from 1 to 2 seconds, as a result of the rise in temperature resulting from absorption of light by said combustible material, within the container, means for supporting the combustible light absorbing material in proximity to the material to be oxidized, a light source outside the transparent container capable of focusing a spot of light on the combustible light absorbing material of sufficient intensity to ignite the combustible light absorbing material in less than 3 seconds, and means for opening and closing the container.

Referring to the drawing, a-convenient transparent container 1 for the apparatus is an Erlenmeyer flask. While the size of the flask is selected as one appropriate for the size of the sample to be oxidized, a wide range of sizes of flasks, and flasks of designs and shapes other than that depicted, are compatible with the invention provided the sample holder 4 with the combustible light absorbing fuse 3 for igniting the sample 5 can be placed near the focal point of the lamp 6. Adjusting the position of the sample holder 4 is facilitated in the embodiment of the invention illustrated in the drawing wherein the means for supporting the sample holder is a glass rod 2 integrally connected to the ball of the ball and socket joint 8 with the lower end shaped into a hook with the rod bent away from the axis of the ball joint to place the hook near the wall of the flask when the ball joint is seated in the socket. When the clamp 9 is loose the ball-arm unit swivels easily in the socket, but when the desired position is reached, tightening the clamp secures the ball in the socket. The ball and socket closure is preferable to the standard taper joint in that there is no tendency for the former to stick as sometimes happens with the tapered joints, however, the latter and other type closures may be used.

Consistent positioning of the sample holder 4 so that the light absorbing material 3 is near the focal point of the lamp 6 is also facilitated by a stop-support 10, a block made of wood or similar material, which is designed to center the flask, to hold the flask at the proper elevation, and to prevent the flask from hitting the lamp.

The combustible light absorbing material 3 (fuse) is preferably paper impregnated with carbon or a black dye free from interfering elements, but may be other material which will ignite in less than 3 seconds when exposed to light beam 7.

A light beam of sufficient intensity to ignite the combustible light absorbing material was obtained with a projection lamp operated by a 5 ampere variable transformer set at 21 volts with the light beam focused on the light absorbing material 3. Other lamps with either internal or external focusing arrangements may be used if the intensity of the light beam is approximately the same or greater than that provided by the projection lamp specified.

Any convenient means of supplying the required current to the light source may be used. In the drawing the current is provided at 11 and the lamp is actuated by closing the circuit with switch 12 while the operator is protected by safety features of both protective shielding 13 and control from a distance.

A specific embodiment of the invention is now described. A 500 ml. Erlenmeyer flask of clear, hard glass (resistant to heat and to thermal shock), as commonly available from all laboratory supply houses, with a 35/25 socket joint was selected as the container. The stopper was made from a 35/25 ball joint, with the ball end closed and a glass rod sealed to the closed end. The other end of the glass rod was shaped into a hook, and

the rod was bent to place the'hook near the wall of the flask when the ball joint was seated in the socket. To correctly position the sample holder so that the lamp would not have to bead 'usted, the hook on each stopper was made the same distance from the bottom of the joint, in this instance a distance of approximately 65 mm. The ball and socket joint is secured with a conventional clamp designed for this purpose.

The sample holder was made from a piece of 20 gauge sheet platinum cut in the shape of a cross, then bent to form a cup 8 mm. inside diameter by 13 mm. high with a handle 1 cm. wide and 3 cm. long. Holes were out in the bottom and walls of the cup to provide ready access of oxygen to the burning sample. A hole at the top of the handle permitted hanging the cup on the glass hook. The sample, contained in a combustible capsule or a folded paper is placed in the cup of the holder. After sample combustion, if desired, as in phosphorus analysis, the detachable sample holder is readily dropped into the absorbing solution by tilting the flask.

The combustible'light absorbing material or fuse was made from White filter paper blackened with india ink. Sudan Black B dye can also be used, or the fuse can be made from Whatman No. 29 black filter paper. The black paper was cut into strips about 6 mm. wide and each fuse was of sufficient length, about '2 cm., so that when insertedin the cup of the sample holder with the capsule or folded paper containing the material to be oxidized, a portion, usually about 1 cm., protruded above the cup at that position where the light beam from the lamp had been prefocused. a

The source of the light beam was a projector lamp, Sylvania Tru-Flector DLG, T14 Lo-volt, operated by a 5 ampere variable transformer, not shown, set at 21 volts. The focused light beam from this source ignited the black fuse in 1 to 2 seconds.

To protect the operator in case of explosion of the flask, combustions are carried out with the lamp and flask in a box about 1 foot per side. The top and hinged front door are of Mr inch thick methyl methacrylate sheet While the sides and back are of 22 gauge metal. The lamp is fastened to one side of the safety box, along with a push button switch and a receptacle for connecting the lamp to the variable transformer. At the bottom of the box below the lamp is a wooden block with a semi-circular indentation about 10 cm. in diameter which aids in positioning the flask with respect to the lamp and prevents the flask from hitting the lamp. Except for the Wooden block the bottom of the box is open.

The apparatus of the present invention is easy to operate d and the analytical results obtained with this apparatus are precise and accurate.

It will be understood that in apparatus of this nature, involving as it does a relatively large number of parts and elements, modifications and other arrangements may be a made Without departing from the principles and scope of the invention which is not limited to the embodiments hcreinabove described and illustrated by Way of example and which is defined by the appended claims.

I claim:

1. An apparatus for carrying out oxygen combustion in a closed container comprising a transparent container, means for holding material to be oxidized within said container, a combustible light absorbing material, capable of igniting in less than 3 seconds as a result of the rise in temperature resulting from absorption of light by said combustible material, within said container, means for supporting said combustible light absorbing material in proximity to the material to be oxidized, alight source outside said container capable of focusing a spot of light on said combustible light absorbing material of sufficient intensity to ignite said combustible light absorbing material in less than 3 seconds, and means of opening and closing said container.

2. An apparatus for carrying out oxygen combustion in a closed container comprising a transparent container, means for holding material to be oxidized within said container, a combustible light absorbing material, capable of igniting within from 1 to 2 seconds as a result of the rise in temperature resulting from absorption of light by said combustible material, within said container, means for supporting said combustible light absorbing material in proximity to the material to be oxidized, a light source outside said container capable of focusing a spot of light on said combustible light absorbing material of snfficient intensity to ignite said combustible light absorbing material within from 1 to 2 seconds, and means for opening and closing said container.

References Cited in the file of this patent UNITED STATES PATENTS 2,809,100 Krasl Oct. 8, 1957 3,058,813 Barney et a1 Oct. 16, 1962 3,058,814 Bennet Oct. 16, 1962 3,107,981

Honma et al Oct. 22, 1963 OTHER REFERENCES 

1. AN APPARATUS FOR CARRYING OUT OXYGEN COMBUSTION IN A CLOSED CONTAINER COMPRISING A TRANSPARENT CONTAINER, MEANS FOR HOLDING MATERIAL TO BE OXIDIZED WITHIN SAID CONTAINER, A COMBUSTIBLE LIGHT ABSORBING MATERIAL, CAPABLE OF IGNITING IN LESS THAN 3 SECONDS AS A RESULT OF THE RISE IN TEMPERATURE RESULTING FROM ABOSORPTION OF LIGHT BY SAID COMBUSTIBLE MATERIAL, WITHIN SAID CONTAINER, MEANS FOR SUPPORTING SAID COMBUSTIBLE LIGHT ABSORBING MATERIAL IN PROXIMITY TO THE MATERIAL TO BE OXIDIZED, A LIGHT SOURCE OUTSIDE SAID CONTAINER CAPABLE OF FOCUSING A SPOT OF LIGHT ON SAID COMBUSTIBLE LIGHT ABSORBING MATERIAL OF SUFFICIENT INTENSITY TO IGNITE SAID COMBUSTIBLE LIGHT ABSORBING MATERIAL IN LESS THAN 3 SECONDS, AND MEANS OF OPENING AND CLOSING SAID CONTAINER. 